Field of the Invention
The present invention generally relates to a circuit board and a manufacturing method thereof. More particularly, the present invention relates to a rigid-flex circuit board and a manufacturing method thereof.
Description of Related Art
Circuit boards include rigid printed circuit boards (short for rigid PCBs), a flexible printed circuit boards (short for FPC boards) and rigid and flexible circuit board (short for rigid-flex circuit board), which are categorized by rigid or flexible characteristics of the dielectric layers thereof. In general, rigid-flex circuit boards are printed circuit boards composed of FPC boards and rigid PCBs, such that the rigid-flex circuit boards can have both the flexibility of the FPC boards and the structural strength of the rigid PCBs. Under the circumstances that inner space of electronic products is rapidly reduced, rigid-flex circuit boards provide maximum flexibility in component connection and assembling space, so rigid-flex circuit boards are often adopted in electronic products as carriers for components.
In manufacturing process, a FPC board having circuit thereon is firstly adopted as a core layer of a rigid-flex circuit board. Then, a cavity is formed on a rigid PCB by routing process. Next, two rigid PCBs are laminated onto two opposite surfaces of the FPC board, such that the cavity of the rigid PCB exposes an exposed region of the FPC board to form the rigid-flex circuit board. However, the routing process has rather low production efficiency and high production cost. Moreover, the process of forming the cavity by routing process would produce scraps, which may cause damages to the FPC board when the rigid PCBs are laminated onto the FPC board. In addition, during the process of laminating the rigid PCBs onto the FPC board, a prepreg of the rigid PCB is easily deformed by compression, such that a part of the prepreg overflows into the cavity and covers the exposed region of the FPC board. As such, the flexibility of the FPC board is significantly reduced since the exposed region is covered by the prepreg. Furthermore, during the process of lamination, the prepreg covering the exposed region is hard to remove and easily causes the problem of gel overflow. Moreover, the process of laminating the rigid PCBs onto the FPC board easily causes misalignment, which effects yield rates of sequential manufacturing process.